Post on 16-Mar-2016
description
Super-Alfvénic ion instabilities and
transportE. Fredrickson for the NSTX
TeamNSTX PAC-19 meeting
Feb. 22-24, 2006Princeton Plasma Physics Laboratory
Culham Sci CtrU St. Andrews
York UChubu UFukui U
Hiroshima UHyogo UKyoto U
Kyushu UKyushu Tokai U
NIFSNiigata UU Tokyo
JAERIHebrew UIoffe Inst
RRC Kurchatov InstTRINITI
KBSIKAIST
ENEA, FrascatiCEA, Cadarache
IPP, JülichIPP, Garching
ASCR, Czech RepU Quebec
College W&MColorado Sch MinesColumbia UComp-XGeneral AtomicsINELJohns Hopkins ULANLLLNLLodestarMITNova PhotonicsNew York UOld Dominion UORNLPPPLPSIPrinceton USNLThink Tank, Inc.UC DavisUC IrvineUCLAUCSDU ColoradoU MarylandU RochesterU WashingtonU Wisconsin
Supported by Office ofScience
NSTX accesses ITER-relevant phase-space island overlap
regime• ITER in new, small * regime for fast ion transport– k ≈ 1 means "short" wavelength Alfvén modes
– fast ion transport from interaction of many modes (MDC-9)
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• NSTX also routinely operates with super-Alfvénic fast ions; q measured in super-Alfvénic ion regime
• 'Avalanch' or 'sea-of-TAE' transport seen• Predicting effect of fast ion transport
on beam driven currents is high priority
Fast ion transport:sFLIP, NPA,
ssNPAneutrons
PredictiveCapability
Analytic
Theory
NSTX can study nonlinear dynamics
Mirnov Array,Soft x-ray cameras
Reflectometer, Interferometer
CHERS (rotation)Equilibrium:MSE, CHERS,Thomson
Scattering
CAE, GAE, TAE, EPM
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EFIT, TRANSP
M3D, HYMNova, HinstOrbit
Physics goals for fast ion physics studies
• 2006 (MSE, sFLIP, ssNPA, polarization diagnostic)– Determination of TAE Avalanche threshold, ORBIT simulations of fast ion losses• Measurement of internal mode amplitude and structure, • together with current profile and fast ion loss measurements
– Validate bootstrap/beam-driven current models • Develop fast -ion MHD-quiescent discharge• Compare J(r) evolution in plasmas with energetic particle MHD
• 2007 (fast FireTip, faster scanning reflectometer?)– Study parameter scaling of mode structure, amplitude, stability and fast ion losses
– Dedicated experiment to compare J(r) evolution with/without fast-ion MHD.
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(To achieve 2007 milestone supporting ITPA MDC-9)
…continued• 2008 - Fast Ion Dalpha (FIDA) diagnostic
– Improved radial profile measurement of Fast Ion MHD induced redistribution
– Continuation EPM/TAE physics studies• Contingency/piggy-back experiments:
– Stochastic heating threshold for CAE/GAE– GAE/CAE phase-space structures (hole-clumps)(Doppler-shifted cyclotron resonance & universal drive)
– External excitation of CAE/GAE (TAE?) – Role of "saturated" EPMs– Non-linear mode coupling (3-wave coupling)
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2006: Experiment to study fast-ion interactions with
TAE and EPM• Test models for EPM-induced fast ion loss:
– Detailed structure of mode, frequency• Test models for EPM stability:
– Bounce or precession-drift resonance?• Study "sea-of-TAE"-induced fast ion losses
– Measurements of multiple mode amplitudes• Test non-linear models of TAE stability
– Avalanche or domino model (Berk, et al., PoP 2 '95, 3007)
• Develop models for non-linear mode interactions (3-wave coupling)
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TAE bursts suggest
"Avalanche" physics• No correlation of repetitive small
bursts; increased amplitude leads to strong multiple mode burst
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• Weak chirping/bursting simulated with M3D-K (Fu)
• Strong bursts consistent with model of "island" overlap in fast ion phase space
• TAE have multiple resonances, more complex physics
Berk, et al., PoP 2 3007
Reflectometer shows "sea of
TAE"
N. Crocker, S. Kubota, W. Peebles, UCLA8
Reflectometer (a.u.)0100200Frequency (kHz)Mirnov Coil #7 (mG)201003210113544_0.2688sn = 1344555667
• Mode amplitude can be used to infer size of phase space island
• Data from before MSE available; great uncertainty in q-profile
• Nova often shows phase inversion - seen for higher n's
1.01.5Major Radius (m)4321050.30.00.20.1Displacement (cm)NSTX 113544_0.2688_117.2kHzqDensity (1013 cm-3)Magnetic AxisPhaseπ0−π
sFLIP data can be used to
benchmark ORBIT simulations
• Relatively new capability
• Pitch angle, energy of lost fast ions is measured
• Loss at highest beam energy, range of pitch angles
• Correlate with ORBIT or M3D/HYM simulations
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9(Fast camera provided by JAERI)
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2006: Validate beam-driven and bootstrap
current models
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• Validate bootstrap/beam driven current physics– Develop fast-ion-MHD-quiescent target plasma– Document current profile evolution with MSE
• Identify stability thresholds for EPM/TAE– Determine MHD-free operational range
• Provides basis for interpretation of effect of TAE/EPM on beam-driven current - feeds into 2007 milestone
Non-linear interactions through
phase space structures
• HHFW stabilization observed– introduces effective collisionality operator on fast ion distribution
– Potential to disrupt avalanch
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CAE: n=8, m=8-10 GAE: n=4, m=2
• Window onto phase space structures in realistic, multi-dimensional phase space.
• HYM code (E. Belova) capable on non-linear CAE/GAE simulations.
NSTX uniquely suited to study non-linear multi-mode
interactions relevant to ITER• NSTX fast ion loss occur with multiple modes, "sea of TAE", as predicted for ITER
• NSTX has comprehensive diagnostic set in the super-Alfvénic fast ion regime
• 2006 experiments address ITPA MDC-9, fast ion redistribution by Alfven modes
• In 2007 will complete experiments to measure effect of TAE/EPM on beam-driven current profile.
• TAE/EPM (CAE) interact, perhaps synergistically– Interactions can be through non-linear phase-space coupling
– Direct non-linear coupling is also being investigated– Study of CAE-induced phase-space structures provide window on realistic, multi-dimensional phase space resonances
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